Apparatus and method for depositing an elongated fiber tow

Abstract

A pressure foot device and system comprising a pressure foot device for guiding, forming and applying an elongate fiber tow, wherein the pressure foot device comprises a foot surface comprising a straight foot segment, a groove comprising a flared end and defining a groove midplane, and a foot shaft housing characterized by a foot shaft's axis of rotation that is orthogonal to the straight foot segment and comprised in the groove midplane.

The invention claimed is: 
     
       1. A pressure foot device for applying an elongate fiber tow onto an object surface, the device comprising:
 a foot surface including a straight foot segment configured to press the fiber tow onto the object surface, the straight foot segment having a rear end and a front end that define a frontal direction from the rear end to the front end; 
 a groove having a left lip and a right lip, configured to guide the fiber tow to the foot surface, the groove defining a groove midplane as a planar portion along a mid-line of the groove and extending between the left lip and the right lip of the groove, the groove joined onto the front end of the straight foot segment; and 
 a tow guide straddling the groove, wherein a distance from the front end of the straight foot segment to the tow guide along the groove midplane is in a range from 2 mm to 30 mm. 
 
     
     
       2. The device of  claim 1 , wherein the tow guide includes a first tow guide segment along a path extending toward the frontal direction from a first side of the pressure foot device with respect to the groove toward the groove midplane and a second tow guide segment along a path extending toward the frontal direction from a second side of the pressure foot device with respect to the groove toward the groove midplane. 
     
     
       3. The device of  claim 2 , wherein the first tow guide segment and the second tow guide segment intersect the groove midplane. 
     
     
       4. The device of  claim 2 , wherein the tow guide has an aperture forming an inverted arch inclined towards the plane comprising the foot surface, a nadir of the inverted arch being located on the groove midplane. 
     
     
       5. The device of  claim 1 , wherein the groove includes a flared end that joins with the foot surface. 
     
     
       6. The device of  claim 1 , wherein the groove includes a flared entry at an end opposite to that reaching the foot surface. 
     
     
       7. The device of  claim 1 , wherein the foot surface includes:
 a first toe surface at a first side of the groove midplane and oriented at a first elevation angle and a first azimuthal angle offset from the frontal direction; and 
 a second toe surface at a second side of the groove midplane and oriented at a second elevation angle and a second azimuthal angle offset from the frontal direction, 
 wherein the first azimuthal angle and the second azimuthal angle are in a range from 30° to 90° with respect to the frontal direction. 
 
     
     
       8. A system for applying an elongate fiber tow onto an object surface, the system comprising:
 a pressure foot device including:
 a foot surface, configured to press the fiber tow onto the object surface, the foot surface including a straight foot segment for pressing the fiber tow onto the object surface, the straight foot segment including a rear end and a front end that define a frontal direction from the rear end to the front end; 
 a groove including a left lip and a right lip, configured for guiding the fiber tow to the foot surface, the groove defining a groove midplane as a planar portion along a mid-line of the groove between the left lip and the right lip of the groove, the groove joined onto the front end of the straight foot segment; and 
 a tow guide straddling the groove, wherein a distance from the front end of the straight foot segment to the tow guide along the midplane of the groove is in a range from 2 mm to 30 mm; and 
 
 a foot shaft housing, having an axis of rotation of the foot shaft, defining a Z-axis, wherein the axis of rotation of the foot shaft is orthogonal to the straight foot segment and within the midplane of the groove. 
 
     
     
       9. The system of  claim 8 , wherein the groove includes a flared end that joins with the foot surface. 
     
     
       10. The system of  claim 8 , wherein the pressure foot device has a hollow foot shaft, the axis of which is collinear with the axis of rotation of the foot shaft and wherein a portion of the shaft forms a sliding fit within the foot shaft housing. 
     
     
       11. The system of  claim 8 , further comprising a source of radiation including infrared radiation directed toward the groove. 
     
     
       12. The system of  claim 8 , further comprising a temperature sensor positioned in one or more of: the foot shaft housing; and the pressure foot device. 
     
     
       13. The system of  claim 8 , further comprising one or more pinch roller assemblies, wherein one or more of the pinch roller assemblies includes a first roller and a second roller, wherein a tangent that is common to the first roller and to the second roller is collinear with the axis of rotation of the foot shaft. 
     
     
       14. The system of  claim 8 , further comprising a robotic support to configure one or more of a position and speed of the pressure foot device at one or more spatial positions and one or more spatial orientations. 
     
     
       15. A method for applying an elongate fiber tow onto an object surface, the method comprising:
 translating an elongate fiber tow into a groove of a pressure foot device unto a foot surface of the pressure foot device, wherein the pressure foot device includes a straight foot segment; 
 the groove including a left lip, a right lip, and defining a groove midplane along a mid-line of the groove and extending until between the left lip and the right lip of the groove; 
 guiding the fiber tow past a tow guide straddling the groove, wherein a distance from a front end of the straight foot segment to the tow guide along the groove midplane is comprised in a range from 2 mm to 30 mm, to the straight foot segment in the foot surface of the pressure foot device, 
 wherein the straight foot segment includes a rear end and a front end that define a frontal direction from the rear end to the front end, and 
 the groove joined onto the front end of the straight foot segment; and 
 pressing the fiber tow between the straight foot segment and the object surface. 
 
     
     
       16. The method of  claim 15 , further comprising guiding the fiber tow within the groove to a flared end of the groove and curving the fiber tow around the flared end of the groove to the straight foot segment. 
     
     
       17. The method of  claim 15 , further comprising guiding the fiber tow within the groove, wherein the step of guiding the fiber tow includes sliding the fiber tow against the tow guide. 
     
     
       18. The method of  claim 15 , wherein the fiber tow within the groove has a cut end. 
     
     
       19. The method of  claim 15 , further comprising one or more of translating and rotating the pressure foot device along a path from a path start to a path end, wherein the straight foot segment is collinear with a tangent to the path of the pressure foot device and a point of tangency to the path is located within the groove midplane. 
     
     
       20. The method of  claim 15 , further comprising unwinding the tow, wherein the step of unwinding includes rotating the pressure foot device.